1. Field of the Invention
The present invention relates to a polygon mirror apparatus with a polygon mirror made using a plastic material, and more particularly, to a polygon mirror apparatus in which a rotor frame and a polygon mirror are formed integrally.
2. Description of the Related Art
Generally, a polygon mirror apparatus is used in a laser scanning unit (LSU) for devices such as a laser printer, a digital copy machine, a barcode reader, and a facsimile machine. The polygon mirror apparatus scans a beam emitted from a light source of the LSU, in a main scan direction, using a rotating polygon mirror.
With the development of technology, print speed of devices using an LSU has increased. Accordingly, the polygon mirror apparatus is required to rotate a polygon mirror at a high speed, and to operate for a long period. In addition, the polygon mirror is required to have a reflectance greater than 85% so as to increase efficiency of a scanning beam. To meet these requirements, conventional polygon mirror apparatus use a polygon mirror manufactured by microprocessing of aluminum that has with a degree of purity of at least 99%.
Referring to FIG. 1, a conventional polygon mirror apparatus includes a base 11, a bearing 13 fixed at the base 11, and a rotating shaft 15 installed at the bearing 13 so as to be rotatable. A rotor frame 17 is coupled with the rotating shaft 15. The apparatus also includes a driving source 20, and a polygon mirror 30 installed at the rotor frame 17.
The driving source 20 is installed at an outer circumference of the bearing 13 and at the rotating shaft 15 so as to rotate the rotating shaft 15 using electromagnetic power. The driving source 20 includes a stator core 21, a rotor housing 23, and a magnet 25. The stator core 21 is fixed at the outer circumference of the bearing 13 and includes a wound coil 22. The rotor housing 23 is coupled with the rotor frame 17 and surrounds the stator core 22.
The polygon mirror 30 is rotated by the driving source 20, thereby deflecting and scanning a beam incident into a reflecting mirror 31 provided on a sidewall of the polygon mirror 30. The polygon mirror 30 is coupled to an outer circumference of the rotor frame 17 and is fixed thereto with a fixing member 35. The polygon mirror 30 is manufactured using an aluminum material with a high degree of purity. The polygon mirror includes reflecting mirrors formed through micromachining of metals.
Since the polygon mirror 30 in the conventional polygon mirror apparatus is manufactured using expensive aluminum material, the manufacturing cost is high. Moreover, since complicated micromachining of metals is used to form the polygon mirror 30, the productivity is low. In addition, a separate rotor frame is used, the polygon mirror is fixed to the rotor frame with a separate fixing member. Thus, the assembly processes are complicated and the number of parts increases.